Electric wave amplifying system



y 35- E. E. HILER 2,002,855

ELECTRIC WAVE AMPLIFYING SYSTEM Filed Aug. 28, 1929 INVEN TOR. YJ flu/0rd Patented May 28, 1935 UNITED STATES PATENT OFFICE 4 Claims.

This invention relates, generally, to electricwave amplifying systems adapted for the detection and amplification of the audio component of electrostatic and electromagnetic energy waves such as received by a radio receiving station; and the invention has reference, more particularly, to the use of electron discharge devices arranged in push-pull relation for accomplishing detection and amplification.

Heretofore, in the detection of the audio component of electrostatic and electromagnetic energy waves it has been common to employ a single electron discharge device as a detector because it has generally been considered impossible to obtain true push-pull detector action. There have been instances where push-pull radio frequency was obtained by arranging detectors in push-pull relation, but such arrangements have failed to obtain the desired push-pull action as regards the audiofrequency component of the received wave. Thus, by using a center tapped radio frequency transformer in the input circuit of a pair of oppositely arranged detector tubes, that portion of the received wave which constitutes the carrier wave or the radio frequency component is passed on to the detector tubes in out of phase relation, that is, the radio frequency voltage impressed on the grid of one detector tube or discharge device during any one voltage cycle is increasing while that impressed on the grid of the other tube is decreasing. However, the audiofrequency components of the two detectors remain in phase since the audiofrequency component of the transmitted carrier wave consists simply of the varying amplitudes of the carrier wave and, while the radio frequency components may be 180 degrees out of phase, the varying amplitudes are still in phase so that as far as the audioirequency component is concerned, the push-pull action is not obtained.

The principal object of the present invention is to provide a novel electric-wave amplifying system having a push-pull detector circuit wherein push-pull action of the audiofrequency component is obtained.

Another object of the invention is to provide a push-pull detector circuit that may be used in conjunction with push-pull audioamplification such as that disclosed in my Patent No. 1,876,674, and other well known types of audioamplification, and which by employing powerful detector tubes is capable of operating a loud speaker directly and without the necessity of employing any intervening stages of audiofrequency amplification.

The use of the novel push-pull detector of this invention substantially eliminates detector tube distortion as well as feed-back or motor-boating, and by employing this novel push-pull detector in conjunction with the push-pull audioamplification system of my above mentioned application, 5 I also do away with audiotube distortion and "B eliminator hum, thereby producing a distortionless, stable and quiet amplifier.

In carrying out the principles of the present invention, a grid rectification detector tube is used in combination with a plate rectification detector tube. In the grid rectification tube, as the amplitude of the carrier Wave increases, the grid of the tube becomes more negative and consequently the audio-component of the plate current in the tube decreases; whereas, in the plate rectification tube, as the amplitude of the carrier wave increases, the grid of the tube becomes more positive and consequently the audio -component of the plate current increases, thereby obtaining pushpull action when properly combined in accordance with the present invention.

ther objects of this invention not at this time more particularly enumerated will be clearly understood from the following detailed description 01 the same.

The invention is clearly illustrated in the accompanying drawing, the single figure of which is a wiring diagram of a push-pull detector circuit embodying the principles of the present invention and used in conjunction with a double impedance push-pull audioamplification system.

Referring now to the said figure, the reference character I designates a radio frequency transformer adapted to have its primary winding connected in a radio frequency amplifier or antenna circuit. A tuning condenser 2 is placed across the secondary winding of the transformer I. One end of this secondary winding is connected by ground connection 3 to the grounded portion of the circuit, whereas the other end of this winding is connected through a coupling condenser 4 to the grid element 5 of a thermionic detector discharge device 6. Discharge device 6 is illustrated as having a filament heated cathode 1 and an anode Ill. The external cathode-grid circuit of device ti extends through a resistance or grid leak 8 which operates in use to lower the potential of the grid 5 with respect to the cathode I. The heating filament 8 of the discharge device 6 is illustrated as heated by alternating current supplied by a generator II, the said generator being coupled in any suitable manner to the filament 9 as by a transformer l2. A resistance I3 is connected across the terminals of the secondary winding of transformer 12 and the mid-point of resistance I3 is connected to the ground connection I4.

The secondary winding of transformer I is also connected directly to the grid element l5 of thermionic detector discharge device l6 having a filament heated cathode ll and an anode or plate 2 l. The external cathode-grid circuit of detector tube i5 extends through a resistance IS, a ground connection !9. ground 3 and the secondary winding of transformer I. The resistance it serves to cause the desired negative bias to be placed upon the grid of tube l5. A condenser 22 is connected across the resistance l8 for by-passing alternating currents. Generator H is illustrated as supplying heating current to the cathode heating filament 23 of tube 06.

The anodes or plates of tubes 6 and ii are respectively connected through condensers 24 and 25 to the respective cathodes of these tubes for the purpose of lay-passing high frequency currents. The plate ll} of tube 6 is connected through a resistance 23 to one outer terminal of a center tapped plate choke coil 21. The other outer terminal of choke coil 2! is connected to the plate 2| of tube IS. The center of choke coil 2'! is connected to a terminal post 23 adapted to be connected to or constituting a B eliminator terminal. Inasmuch as any suitable 13" eliminator may be employed for this purpose and as the same forms no part of the present invention it is not shown in the drawing. The use of the resistance 25 enables the application of a lower plate voltage to tube 5 than that applied to tube 16. A condenser 23 is connected across the terminals of resistance 26 to enable the passage of audiofrequency currents.

Since detector tube 5 is connected for grid rectification whereas detector tube l 5 is connected for plate rectification, the fundamental audio currents in the plate circuits of these tubes differ by 180 degrees. ()wing to the manner of connecting the plates of these tubes to the choke coil 27, the magnetic fields set up by the fundamental plate circuit currents of these tubes in coil 21 are additive while those set up by the harmonics are opposed and oiiset each other.

The plate of tube 5 is connected through condenser 29 and a coupling condenser 3| to the grid of an audioamplification thermionic device or tube 32 arranged in opposition or push-pull relation with a similar tube 33. The plate 2! of tube 16 is connected through a. coupling condenser 34 to the grid of tube 33. A center tapped grid choke coil 35 is connected between the grid input circuits of tubes 32 and 33 and has its center tap grounded at 35. The external cathode-grid circuit of tube 32 extends through a grid biasing resistance 31 and the'upper half of grid choke coil 35, whereas the external cathode-grid circuit of tube 33 extends through resistance 31 and the lower half of grid choke coil 35. A condenser 38 is connected across resistance 37 for bypassing alternating currents. The cathode heating filaments of tubes 32 and 33 are shown as supplied with heating current from the generator ll.

The plates or anodes of tubes 32 and 33 are connected to the outer terminals of a center tapped plate choke coil 39. The center of choke coil 39 is connected to a terminal post H of a suitable B eliminator terminal. Owing to the push-pull arrangement of tubes 32 and 33, though the fundamental currents in the plate circuits of these tubes differ by 180 degrees, yet the magnetic fields set by these currents in the choke coil 39 are additive while those set up by the harmonics are opposed and offset from each other.

The plate of tube 32 is connected through a coupling condenser 42 to the grid of a tube 43 arranged in opposition or push-pull relation with a similar tube 44. The plate of tube 33 is connected through a coupling condenser to the grid of tube 44. A center tapped grid choke coil 46 is connected between the grid input circuits of tubes 43 and 44 and has its center tap grounded at 4?. The external cathode-grid circuit of tube 43 extends through a resistance 48 and the upper half of grid choke coil 46, whereas the external cathode-grid circuit of tube 44 extends through resistance 48 and the lower half of grid choke coil 46. A condenser 49 is connected across resistance 48. The cathode heating filaments of tubes 43 and 44 are also shown as supplied with heating current from generator II.

The plate or anodes of tubes 43 and 44 are connected to the outer terminals of a center tapped plate choke coil 5! having its center tap connected to the B eliminator terminal post 52. The plates of these tubes are respectively conneced through coupling condensers 53 and 54 to the respective grids of thermionic devices 55 and 55 arranged in opposition or push-pull relation. A center tapped grid choke coil 5? is connected between the grid input circuits of tubes 55 and 56 and has its center tap grounded at 53.

The electron discharge devices 55 and 53 are illustrated as having filamentary cathodes which are shown as heated by A. C. supplied by a generator 59 through a transformer 6!. A resistance 62 is connected across the terminals of the secondary winding of transformer 61, and the midpoint of resistance 52 is connected through a grid biasing resistance 53 to ground 64. A condenser is connected across resistance 63 for by-passing alternating currents.

The external filament-grid circuit of tube 55 extends through resistance 63, ground 64 and 58 and the upper half of grid choke coil 5?, whereas the corresponding circuit of tube 56 extends through resistance 63, grounds 64 and 58 and the lower half of grid choke coil 5?.

The plates or anodes of tubes 55 and 55 are connected to the outer terminals of a center tapped output choke coil 65. The center tap of choke coil 65 is illustrated as connected to a B eliminator terminal post 55. A loud speaker or telephone 61 is illustrated as connected in shunt across the terminals of choke coil 55.

In operation, the tuned circuit l-2 causes an alternating carrier wave potential to be impressed upon each of the grids 5 and i5 which potentials have substantially the same phase and magnitude. Since tube 6 is connected for grid rectification. as the amplitude of the carrier wave increases. the grid 5 becomes more negative and consequently the audiofrequency component of the current flowing in the plate circuit of tube 5 decreases; whereas, since tube i5 is connected for plate rectification, as the amplitude of the carrier wave increases, the grid 15 becomes more positive and, consequently the audiofrequency component of the current flowing in the plate circuit of the tube l6 increases, thereby causing the audiofrequency components of the plate currents of these two tubes to be additive in their magnetic effects in the choke coil 21, whereas harmonics delivered by these tubes are in phase and therefore are balanced out. Radio frequency currents are shunted out of the plate circuits of tubes 8 and I6 by condensers 24 and 25 respectively.

Since condenser 3i and the upper half of choke coil are connected in shunt with the upper half of choke coil 21 through the B eliminator, an alternating current potential of substantially the same value as impressed across the upper half of coil 21 is impressed upon the upper half of coil 35 since there is but little drop in potential across condensers 29 and 3!. An alternating current potential is therefore applied to the grid of electron discharge device 32. Also, since condenser 34 and the lower half of choke coil 35 are connected in shunt with the lower half of coil 21 through the "B eliminator, an alternating current potential of substantially the same value as impressed across the lower half of coil 21 is impressed upon the lower half of coil 35 causing an alternating current potential to be applied to the grid of electron discharge device 33.

Since the audiofrequency components of the plate currents of tubes 6 and I6 are substantially I8!) degrees out of phase, the potentials impressed on the grids of devices 32 and 33 will also be substantially 130 degrees out of phase causing the plate currents of these tubes to be likewise out of phase but nevertheless additive in their magnetic effect in the choke coil 39.

The fundamental signals delivered by tubes 32 and 33 are amplified by tubes 43 and M and are delivered to tubes 55 and 56 for further amplification. Obviously a lesser or greater number of stages of audioampliiication than those disclosed in this application may be employed for amplifying the fundamental signals. The fundamental output currents of tubes 55 and 56 are likewise additive in the output choke coil 65 while harmonies are cancelled out, the fundamental currents acting to operate speaker or phones 81.

It is to be understood that although the novel push-pail detector circuit of this invention is illustrated in conjunction with an audioamplification system, yet nevertheless when employing a sufiiciently powerful output signal and detector tubes 6 and iii, the speaker 61 may be connected directly across choke coil 21 or across the terminals of a transformer or other suitable network, thereby operating the speaker without distortion owing to the elimination of the harmonics generated in the detector tubes.

Since extraneous B eliminator A. C. voltages which would tend to produce a hum at the speaker 51, are delivered to the center taps of coils 21, 39, 5| and E5 and as these currents divide flowing in opposite directions through these coils, the magnetic fields of these currents in the halves of the coils are opposed and balance out, thereby eliminating hum and iron core saturation. This is likewise true of feed backs which are thus prevented from producing tube oscillation or distor tion.

Although the electrodes of the thermionic devices are illustrated as supplied with energy from alternating current sources, it is to be understood that direct current supply may be used if desired.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In an electric-wave amplifying system, the combination of detector electron discharge devices, each of said devices having a grid element together with a cathode and anode, means for controlling the grids of said devices whereby one of said devices detects by grid rectification and another by plate rectification, external circuits extending between the anodes and cathodes of said devices, and an inductive reactance element having portions thereof respectively included in each of said external circuits.

2. In an electric-wave amplifying system, the combination of detector electron discharge devices, each of said devices having a grid element together with a cathode and anode, external circuits extending between the cathodes and grids of said devices, impedance means included in said external circuits for controlling the grids of said devices, whereby one of said devices detects by grid rectification and another by plate rectification, each of said devices having an external anode-cathode circuit, anode impedance means having portions thereof respectively included in said anode-cathode circuits and through wh ch positive potential is adapted to be supplied to the anodes of said pair of discharge devices, an audioamplifier, and condenser means adapted to couple said anode-cathode circuits to said audioarnplifier.

3. In an electric-wave amplifying system, the combination of a pair of detector electron discharge devices, each of said devices having a grid element together with a cathode and anode, means for controlling said devices whereby one of said devices detects by grid rectification and the other by plate rectification, external cir cuits extending between the anodes and cathodes of said devices, anode impedance means through which positive potential is adapted to be supplied to the anodes of said pair of discharge devices. a pair of condensers and an inductive reactance element conjoined and arranged in parallel with said anode impedance means, and a second pair of electron discharge devices, each of said latter devices having its grid element connected to one of said condensers.

4. In an electric-wave amplifying system. the combination of detector electron discharge devices, each of said devices having a grid element together with a cathode and anode, an input circuit electrically connected to the grid elements of said devices so that signal potentials emanating from said input circuit are impressed on the grids of said devices, means for controlling the grids of said devices whereby one of said devices detects by grid rectification and another by plate rectification, means for energizing the cathodes of said devices, external circuits extending between the anodes and cathodes of said devices, and an inductive reactance element having portions thereof respectively included in each of said external circuits and through which posi tive potential is supplied to the anodes of said devices.

EDWARD E. HILER. 

